What is the difference between ps and top command?

I was going through the help page of ps command (using ps --h) and I noticed the two options have the same description.

-e all processes -A all processes

I ran the commands with both the options and I noticed no difference.

Is there any difference between the two options? If not why to provide two options that does the same?

I was trying to figure out difference between

gnome-screensaver-command -a

and

gnome-screensaver-command -l

According to the gnome-screensaver-command man page...

-l, --lock Tells the running screensaver process to lock the screen immediately -a, --activate Turn the screensaver on (blank the screen)

For me in both the cases it generated the login screen.Can s

Hi,

Can someone tell me what the difference is between ps -ef and ps aux. I was under the assumption that both commands would list ALL processes currently running on the system.

But on my server I find the following:

Code:

# ps  -ef | wc -l     519 # ps aux | wc -l     571 What are these 52 processes found by aux?

When I send a command to a remote server over ssh what is the difference between:

ssh user@123.456.789.012 'foo'

and

ssh user@123.456.789.012 "foo"

I am not passing any variables, and I am getting different results when running a command remotely.

CentOS 6.3 / RHEL 6.3

Can someone please explain the difference between the whatis command and the apropos command? I noticed that both appear to be installed by default and I'm not sure what the difference is between them.

I'm wondering what's the difference between "man 3 command" vs "man command"?

I read in wiki (http://en.wikipedia.org/wiki/Man_page) that man 3 is used in Linux in section 3 of the man pages. And section 3 refers to Library functions, covering in particular the C standard library.

Is there any difference between using update manager from main menu and using the commands Code: sudo apt-get update && sudo apt-get upgrade from a terminal?

I have the following command running on cron:

sudo find "$VOLUME1" "$VOLUME2" "$VOLUME3" "$VOLUME4" -type f -exec ls -lT {} + > $FILE

This command takes a couple hours to complete, as it's running over about million files or so.

When I do the top command, it shows 14(!!) difference instances of ls running. Is this a bug in the script, or what is causing so many ls commands to be running?

First command

sudo dd if=/dev/zero of=/dev/sda

second command

sudo dd if=/dev/zero of=/dev/sda bs=1M

I am formatting my pc for 4 hours with first code but it didn't finish. Please help me.

Is the first code wrong?

What is the difference?